Mesoscale Numerical Simulation of a Downburst

2011 ◽  
Vol 243-249 ◽  
pp. 5029-5032
Author(s):  
Yi Fei Wang ◽  
Wei Lian Qu ◽  
Bin Wang ◽  
Yan Li ◽  
Bai Feng Ji
Keyword(s):  
Numerical Simulation ◽  
Meteorological Factors ◽  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Point Of View ◽  
Wind Engineering ◽  
Small Scale ◽  
Engineering Structures ◽  
The World ◽  
Simulation Results

Downburst winds with their great destructive power have caused destruction of numerous engineering structures around the world. Study on wind loadings of downburst is essential and hot in the wind engineering field. But various meteorological factors of downburst formulation are not considered in existing research methods in the wind engineering field. In this paper, a downburst case is simulated by using a numerical weather prediction model ARPS from the meteorological point of view. The simulation results successfully reproduce the wind field characteristics while downburst occurring. The study in this paper aims at introducing meteorological method and knowledge to the wind engineering field, and the results of mesoscale numerical simulation in this study will be used in the small-scale numerical simulation as initial data in further study.

Characteristics of Heat Transfer and Flow on a Surface With Small-Scale Concave Spherical Pits

2008 ◽  
Author(s):  
J. S. Wang ◽  
Y. Qiu ◽  
L. Y. Li
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Small Scale ◽  
Heat Transfer Mechanism ◽  
Transfer Enhancement ◽  
Special Effect ◽  
Turbulent Drag Reduction ◽  
Turbulent Drag ◽  
Simulation Results ◽  
Turbulent Coherent Structure

Small-scale concave spherical pits, which have a special effect on heat transfer enhancement and turbulent drag reduction, are investigated by numerical simulation in detail. Two kinds of small-scale concave pits structures are designed on surface of a plate, which are located in the bottom of a rectangle channel. The characteristics of heat transfer and flow in channel are investigated and compared with a same channel with plate bottom by means of LES. Flow structure and temperature distribution near the pits are analyzed. The numerical simulation results indicate that the concave spherical pits disturb the flow field and vortex is induced by the pits. The turbulent coherent structure is affected by the induced vortex. The numerical simulation indicates that small scale pit can generate the vortex in couple. The range of vortex is accord with the array of small scale pit. The small scale pit can enhance the intensity of vortex. As a result, the temperature field near the pit is changed with generation of the vortex. The heat transfer mechanism on plate with small scale concave spherical pit is summarized.

scholarly journals Detection and thermal description of medicanes from numerical simulation

2014 ◽  
Vol 14 (5) ◽  
pp. 1059-1070 ◽  
Author(s):  
M. A. Picornell ◽  
J. Campins ◽  
A. Jansà
Keyword(s):  
Numerical Simulation ◽  
Thermal Structure ◽  
Weather Prediction ◽  
Weather Forecast ◽  
Small Scale ◽  
Medium Range Weather Forecast ◽  
Warm Core ◽  
Strong Winds ◽  
Nwp Model ◽  
Ecmwf Model

Abstract. Tropical-like cyclones rarely affect the Mediterranean region but they can produce strong winds and heavy precipitations. These warm-core cyclones, called MEDICANES (MEDIterranean hurriCANES), are small in size, develop over the sea and are infrequent. For these reasons, the detection and forecast of medicanes are a difficult task and many efforts have been devoted to identify them. The goals of this work are to contribute to a proper description of these structures and to develop some criteria to identify medicanes from numerical weather prediction (NWP) model outputs. To do that, existing methodologies for detecting, characterizating and tracking cyclones have been adapted to small-scale intense cyclonic perturbations. First, a mesocyclone detection and tracking algorithm has been modified to select intense cyclones. Next, the parameters that define the Hart's cyclone phase diagram are tuned and calculated to examine their thermal structure. Four well-known medicane events have been described from numerical simulation outputs of the European Centre for Medium-Range Weather Forecast (ECMWF) model. The predicted cyclones and their evolution have been validated against available observational data and numerical analyses from the literature.

Numerical Simulation of Small-Scale Explosion in Dry Sand

2013 ◽  
Vol 705 ◽  
pp. 110-114
Author(s):  
Yu Qing Ding ◽  
Wen Hui Tang ◽  
Xian Wen Ran ◽  
Xin Xu
Keyword(s):  
Numerical Simulation ◽  
Test Data ◽  
Detonation Product ◽  
Material Model ◽  
Small Scale ◽  
Two Dimensional ◽  
Material Models ◽  
Simulation Results ◽  
Dry Sand ◽  
Sand Material

Numerical simulation of small-scale explosion in dry sand using two sand material models including the Sand model and the LA model were carried out in the present study. Three cases were considered which the depths of burial (DOB) of the explosive C4 charge were 0, 30 mm and 80 mm, respectively. The time arrival of the blast-wave front and the maximum overpressure of fixed measuring locations were studied using a two dimensional axisymmetric model in hydrocode ANSYS/AUTODYN. Furthermore, the crater diameters and the heights of detonation product cloud respect to the time were also studied by comparing with the test data. The simulation results indicate that the both sand material models were hardly predict the test data exactly which proves that the sand properties and the material model should be more carefully studied and defined.

scholarly journals Does the Representation of Flow Structure and Turbulence at a Cold Front Converge on Multiscale Observations with Model Resolution?

2017 ◽  
Vol 145 (11) ◽  
pp. 4345-4363 ◽  
Author(s):  
Ben Harvey ◽  
John Methven ◽  
Chloe Eagle ◽  
Humphrey Lean
Keyword(s):  
Flow Structure ◽  
Cold Front ◽  
Spatial Scales ◽  
Weather Prediction ◽  
Turbulent Fluxes ◽  
Numerical Weather Prediction Model ◽  
Shear Instability ◽  
Small Scale ◽  
Convective Boundary ◽  
Direct Evaluation

In situ aircraft observations are used to interrogate the ability of a numerical weather prediction model to represent flow structure and turbulence at a narrow cold front. Simulations are performed at a range of nested resolutions with grid spacings of 12 km down to 100 m, and the convergence with resolution is investigated. The observations include the novel feature of a low-altitude circuit around the front that is closed in the frame of reference of the front, thus allowing the direct evaluation of area-average vorticity and divergence values from circuit integrals. As such, the observational strategy enables a comparison of flow structures over a broad range of spatial scales, from the size of the circuit itself ([Formula: see text]100 km) to small-scale turbulent fluctuations ([Formula: see text]10 m). It is found that many aspects of the resolved flow converge successfully toward the observations with resolution if sampling uncertainty is accounted for, including the area-average vorticity and divergence measures and the narrowest observed cross-frontal width. In addition, there is a gradual handover from parameterized to resolved turbulent fluxes of moisture and momentum as motions in the convective boundary layer behind the front become partially resolved in the highest-resolution simulations. In contrast, the parameterized turbulent fluxes associated with subgrid-scale shear-driven turbulence ahead of the front do not converge on the observations. The structure of frontal rainbands associated with a shear instability along the front also does not converge with resolution, indicating that the mechanism of the frontal instability may not be well represented in the simulations.

Gridded Operational Consensus Forecasts of 2-m Temperature over Australia

2012 ◽  
Vol 27 (2) ◽  
pp. 301-322 ◽  
Author(s):  
Chermelle Engel ◽  
Elizabeth E. Ebert
Keyword(s):  
Bias Correction ◽  
Statistical Approach ◽  
Weather Prediction ◽  
Weighted Average ◽  
Numerical Weather Prediction Model ◽  
Small Scale ◽  
Coarse Scale ◽  
Consensus Forecasts ◽  
Average Consensus ◽  
Almost All

Abstract This paper describes an extension of an operational consensus forecasting (OCF) scheme from site forecasts to gridded forecasts. OCF is a multimodel consensus scheme including bias correction and weighting. Bias correction and weighting are done on a scale common to almost all multimodel inputs (1.25°), which are then downscaled using a statistical approach to an approximately 5-km-resolution grid. Local and international numerical weather prediction model inputs are found to have coarse scale biases that respond to simple bias correction, with the weighted average consensus at 1.25° outperforming all models at that scale. Statistical downscaling is found to remove the systematic representativeness error when downscaling from 1.25° to 5 km, though it cannot resolve scale differences associated with transient small-scale weather.

scholarly journals Sensitivity experiments of a severe rainfall event in north-western Italy: 17 August 2006

2008 ◽  
Vol 2 (1) ◽  
pp. 133-138 ◽  
Author(s):  
M. Milelli ◽  
E. Oberto ◽  
A. Parodi
Keyword(s):  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Precipitation Forecast ◽  
Small Scale ◽  
Moist Convection ◽  
Cosmo Model ◽  
Quantitative Precipitation Forecast ◽  
Scale Modelling ◽  
North Western ◽  
Priority Project

Abstract. This study is embedded into a wider project named "Tackle deficiencies in Quantitative Precipitation Forecast (QPF)'' in the framework of the COSMO (COnsortium for Small-scale MOdelling) community. In fact QPF is an important purpose of a numerical weather prediction model, for forecasters and customers. Unfortunately, precipitation is also a very difficult parameter to forecast quantitatively. This priority project aims at looking into the COSMO Model deficiencies concerning QPF by running different numerical simulations of various events not correctly predicted by the model. In particular, this work refers to a severe event (moist convection) happened in Piemonte region during summer 2006. On one side the results suggest that details in orography representation have a strong influence on accuracy of QPF. On the other side COSMO Model exhibits a poor sensitivity on changes in numerical and physical settings when measured in terms of QPF improvements. The conclusions, although not too general, give some hint towards the behaviour of the COSMO Model in a typical convective situation.

scholarly journals Perceptions and Role of Tourist Destination Residents Compared to Other Event Stakeholders in a Small-Scale Sports Event. The Case of the FIS World Junior Alpine Ski Championships 2019 in Val di Fassa

2019 ◽  
Vol 11 (24) ◽  
pp. 6909 ◽  
Author(s):  
Filippo Bazzanella
Keyword(s):  
Sustainable Development ◽  
Qualitative Method ◽  
Point Of View ◽  
Small Scale ◽  
Tourist Destination ◽  
The Sustainable Development ◽  
Sports Events ◽  
The World

The role of stakeholders is critical in addressing challenges with or problems in small-scale sports events. The purpose of this study is to investigate the perceptions of the event stakeholders toward sports events, with a particular focus on the role of residents in a tourist destination. The goal is to understand their perceptions with respect to different topics and in particular to the sustainable development of the tourist destination. This case study focuses on the World Junior Alpine Ski Championships 2019 in Trentino Val di Fassa—Italy (JWC2019). Applying a mixed methodology, the study analyzes the stakeholders during the sports event (quantitative method) and the point of view of the residents in their stakeholder role after the sports event (qualitative method). The main findings of this study show that residents differ from tourists and other stakeholders in terms of their perception of the event and its strengths. But when it comes to the perceptions regarding the territory, the groups of stakeholders analyzed do not seem to have systematically different opinions. Some paradoxes do, however, emerge with respect to the residents’ awareness of their role as stakeholders and the implications of the event with respect to sustainability and how such an event may underpin a concept of sustainable development for the territory as a whole.

Deference, Degree and Selfhood

Philosophy ◽  
2005 ◽  
Vol 80 (2) ◽  
pp. 249-260
Author(s):  
Stephen R. L. Clark
Keyword(s):  
Point Of View ◽  
Small Scale ◽  
Liberal Ideal ◽  
Egalitarian Society ◽  
The World

The world we lost, and now barely understand, was one where everyone knew her place, and her attendant duties. Civilized groups were the likeliest to insist on a diversity of rôle and rule. Primitive societies are ones where there are rather fewer such distinctions. Slaves and merchants offered a way of being outside the orders, and from the older point of view, the life of slaves and merchants is exactly what the ‘liberal’ ideal entails. No one can count on her connections; everything is up for sale; no one is dishonoured by the acts of friends or family; only animal passions keep us all together. Even in societies that profess egalitarian theories, castes and classes re-emerge. If there is another option it may lie in drawing, as the ancients did, a clear division between selfhood and nature: even in a traditionally hierarchical society it is possible to recall the mere selves that play their various parts. In a would-be egalitarian society that hopes for something more than the hedonic or agonistic bonds that may bind small-scale communities together, recalling, and reconstructing, that distinction may be even more important.

scholarly journals Detection and thermal description of medicanes from numerical simulation

2013 ◽  
Vol 1 (6) ◽  
pp. 7417-7447 ◽  
Author(s):  
M. A. Picornell ◽  
J. Campins ◽  
A. Jansà
Keyword(s):  
Numerical Simulation ◽  
Mediterranean Region ◽  
Thermal Structure ◽  
Weather Prediction ◽  
Small Scale ◽  
Warm Core ◽  
Detection And Tracking ◽  
Strong Winds ◽  
Nwp Model ◽  
Ecmwf Model

Abstract. Tropical-like cyclones rarely affect the Mediterranean region and they can produce strong winds and heavy precipitations. These warm-core cyclones, called MEDICANES (MEDIterranean hurriCANES), are small size, develop over the sea and are infrequent. For these reasons, the detection and forecast of medicanes are a difficult task and many efforts have been devoted to identify them. The goals of this work are to contribute to a proper description of these structures and to develop some criteria to identify medicanes from numerical weather prediction (NWP) model outputs. To do that, existing methodologies for detecting, characterizating and tracking cyclones have been adapted to small-scale intense cyclonic perturbations. First, a mesocyclone detection and tracking algorithm has been modified to select intense cyclones. Next, the parameters that define the Hart's cyclone phase diagram are tuned and calculated to examine their thermal structure. Four well-known medicane events have been described from numerical simulation outputs of the ECMWF model. The predicted cyclones and their evolution have been validated against available observational data and numerical analyses from literature.

MOS, Perfect Prog, and Reanalysis

2006 ◽  
Vol 134 (2) ◽  
pp. 657-663 ◽  
Author(s):  
Caren Marzban ◽  
Scott Sandgathe ◽  
Eugenia Kalnay
Keyword(s):  
Mean Squared Error ◽  
Weather Prediction ◽  
Error Variance ◽  
Numerical Weather Prediction Model ◽  
Reanalysis Data ◽  
Point Of View ◽  
Model Output ◽  
Squared Error ◽  
Error Bias ◽  
Model Output Statistics

Abstract Statistical postprocessing methods have been successful in correcting many defects inherent in numerical weather prediction model forecasts. Among them, model output statistics (MOS) and perfect prog have been most common, each with its own strengths and weaknesses. Here, an alternative method (called RAN) is examined that combines the two, while at the same time utilizes the information in reanalysis data. The three methods are examined from a purely formal/mathematical point of view. The results suggest that whereas MOS is expected to outperform perfect prog and RAN in terms of mean squared error, bias, and error variance, the RAN approach is expected to yield more certain and bias-free forecasts. It is suggested therefore that a real-time RAN-based postprocessor be developed for further testing.

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